Reactive coatings comprising an acid-functional compound, an anhydride-functional compound and an epoxy-functional compound

ABSTRACT

Coating compositions which comprise: 
     (i) an acid-functional compound having an average of at least two carboxylic acid groups per molecule; and 
     (ii) an anhydride-functional compound having an average of at least two cyclic carboxylic acid anhydride groups per molecule; and 
     (iii) an epoxy-functional compound having an average of at least one epoxy group per molecule; wherein at least one of the compounds (i), (ii), or (iii) comprises a film forming polymer.

This is a continuation of application Ser. No. 07/763,036 filed on Sep.20, 1991, now abandoned, which is divisional of application Ser. No.07/120,893 filed on Nov. 16, 1987, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel reactive coatings which can be cured atroom temperature or force dried at temperatures ranging up to about 350°F. The coatings may be utilized as primers, topcoats or as clearcoatsand/or basecoats in clearcoat/basecoat compositions. The combination ofacid-functional compounds, anhydride-functional compounds, andepoxy-functional compounds, especially cycloaliphatic epoxy compounds,provides fast reacting, durable coatings which minimize the toxicityproblems which may be associated with other low temperature curingsystems.

2. Description of the Prior Art

Many prior art approaches to high performance low temperature curingcoatings have involved two component coatings comprising reactivepolyisocyanates and active hydrogen-containing compounds such ashydroxyl-containing polymers or amine-containing polymers to producepolyurethane or polyurea coatings. Although these materials haveexcellent performance and cure at low temperatures, the isocyanates may,under some conditions, be relatively hazardous to handle.

Coating compositions comprising reactive combinations ofepoxy-containing compounds and compounds having acid or aminefunctionality are known in the art. Similarly, coating compositionscomprising cyclic anhydrides and epoxy-functional compounds are alsoknown in the art. The prior art has not, however, taught the combinationof anhydride-functional compounds, acid-functional compounds, andepoxy-functional compounds to provide low temperature curing coatingshaving excellent durability and performance.

BRIEF SUMMARY OF THE INVENTION

This invention involves a curable composition which comprises: (i) anacid-functional compound having an average of at least two carboxylicacid groups per molecule; and (ii) an anhydride-functional compoundhaving an average of at least two cyclic carboxylic acid anhydridegroups per molecule; and (iii) an epoxy-functional compound having anaverage of at least one and, preferably, at least two epoxy groups permolecule; wherein at least one of the compounds (i), (ii) or (iii)comprises a film forming polymer. The term "compound" is used in itsbroadest sense to include monomers, oligomers and polymers. The term"film forming polymer" means any polymeric material that can form a filmfrom evaporation of any carrier or solvent.

In its more preferred formulation, this invention relates to curablecompositions wherein the acid-functional compound is a polymer obtainedby the half-ester reaction of a hydroxy-functional polymer with a cycliccarboxylic acid anhydride, and wherein the anhydride-functional compoundis the addition polymerization product of at least one unsaturatedmonomer having anhydride functionality and at least one otherethylenically unsaturated monomer, and wherein the epoxy-functionalcompound is a cycloaliphatic epoxy compound.

It is especially preferred to utilize the curable compositions of thisinvention in combination with about 5 to about 80%, and especially 5 toabout 50%, by weight of an inert solvent, such as esters, ketones,aromatic and aliphatic hydrocarbons, etc. It is convenient to providethe coating composition as a multi-component system which is reactiveupon mixing the components. Especially preferred is a two-componentsystem wherein the anhydride-functional compound and the acid-functionalcompound are combined in one package and the epoxy-functional compoundprovides a second package. The two components can then be mixed togetherto provide the curable coatings immediately prior to application.

In one preferred application, this invention relates to coatedsubstrates having a multi-layer decorative and/or protective coatingwhich comprises:

(a) a basecoat comprising a pigmented film-forming polymer; and

(b) a transparent clearcoat comprising a film-forming polymer applied tothe surface of the basecoat composition;

wherein the clearcoat and/or the basecoat comprises the curablecompositions of this invention.

Accordingly, it is an object of this invention to provide improvedcurable compositions having excellent reactivity at low temperatures. Itis a further object of this invention to provide coating compositionswhich may be utilized as primers, topcoats or clearcoats and/orbasecoats in clearcoat/basecoat compositions. Another object of thisinvention is to provide an improved two-package coating compositionwherein one package comprises an anhydride-functional compound and anacid-functional compound and the other component comprises aepoxy-functional compound. Another object of this invention is toprovide coatings having excellent exterior durability and corrosionresistance. A further object of this invention is to provide improvedcoating compositions which can be cured at room temperature or forcedried at elevated temperatures. These and other objects of the inventionwill become apparent from the following discussions.

DETAILED DESCRIPTION OF THE INVENTION 1. Acid-Functional Compounds

The acid-functional compounds which are useful in the practice of thisinvention should have an average of at least two, and preferably atleast three, carboxylic acid groups per molecule. Although low molecularweight diacids and polyacids such as phthalic acid, succinic acid,adipic acid, azelaic acid, maleic acid, fumaric acid, trimellitic acidand trimesic acid can be utilized in the practice of this invention, itis especially preferred to utilize polymeric acid-functional compounds.

Preferably the acid-functional polymer will have a number averagemolecular weight of at least about 400 and most preferably at least1,000. Typical number average molecular weights of the carboxylicacid-functional polymers will range from about 1,000 to about 30,000.Representative acid-functional polymers include acrylics, polyesters andpolymers prepared by the reaction of anhydrides with hydroxy-functionalpolymers as discussed more fully below.

1.A. Carboxylic Acid-Functional Polymers Prepared by the Half-EsterForming Reaction of Anhydrides and Hydroxy-Functional Polymers

Especially preferred in the practice of this invention are carboxylicacid-functional polymers prepared by the half-ester reaction of cycliccarboxylic acid anhydrides and hydroxy-functional polymers. Thehalf-ester reaction involves the ring opening of the cyclic anhydride byreaction with a hydroxyl group on the hydroxy-functional polymer to formone ester group and one acid group.

Typically, the hydroxy-functional polymers will have number averagemolecular weights of at least about 400, preferably at least 1,000, andtypical number average molecular weights will range from about 400 toabout 30,000, and especially 1,000 to about 15,000. Methods of preparinghydroxy-functional polymers are well known in the art and the method ofpreparation of the hydroxy-functional molecule or polymer is notcritical to the practice of this invention. Representative polymerswhich can be reacted with anhydrides to produce the acid-functionalpolymers include the hydroxy-functional polyethers, polyesters,acrylics, polyurethanes, polycaprolactones, etc. as generally discussedin Sections 1A.1. through 1.A.5. below.

1.A.1. Polyether polyols are well known in the art and are convenientlyprepared by the reaction of a diol or polyol with the correspondingalkylene oxide. These materials are commercially available and may beprepared by a known process such as, for example, the processesdescribed in Encyclopedia of Chemical Technology, Volume 7, pages257-262, published by Interscience Publishers, Inc., 1951.Representative examples include the polypropylene ether glycols andpolyethylene ether glycols such as those marketed as Niax® Polyols fromUnion Carbide Corporation.

1.A.2. Another useful class of hydroxy-functional polymers are thoseprepared by condensation polymerization reaction techniques as are wellknown in the art. Representative condensation polymerization reactionsinclude polyesters prepared by the condensation of polyhydric alcoholsand polycarboxylic acids or anhydrides, with or without the inclusion ofdrying oil, semi-drying oil, or non-drying oil fatty acids. By adjustingthe stoichiometry of the alcohols and the acids while maintaining anexcess of hydroxyl groups, hydroxy-functional polyesters can be readilyproduced to provide a wide range of desired molecular weights andperformance characteristics.

The polyester polyols are derived from one or more aromatic and/oraliphatic polycarboxylic acids, the anhydrides thereof, and one or morealiphatic and/or aromatic polyols. The carboxylic acids include thesaturated and unsaturated polycarboxylic acids and the derivativesthereof, such as maleic acid, fumaric acid, succinic acid, adipic acid,azelaic acid, and dicyclopentadiene dicarboxylic acid. The carboxylicacids also include the aromatic polycarboxylic acids, such as phthalicacid, isophthalic acid, terephthalic acid, etc. Anhydrides such asmaleic anhydride, phthalic anhydride, trimellitic anhydride, or NadicMethyl Anhydride (brand name formethylbicyclo[2.2.1]heptene-2,3-dicarboxylic anhydride isomers) can alsobe used.

Representative saturated and unsaturated polyols which can be reactedwith the carboxylic acids to produce hydroxy-functional polyestersinclude diols such as ethylene glycol, dipropylene glycol,2,2,4-trimethyl 1,3-pentanediol, neopentyl glycol, 1,2-propanediol,1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol,1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol,1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-bis(2-hydroxyethoxy)cyclohexane, trimethylene glycol, tetramethyleneglycol, pentamethylene glycol, hexamethylene glycol, decamethyleneglycol, diethylene glycol, triethylene glycol, tetraethylene glycol,norbornylene glycol, 1,4-benzenedimethanol, 1,4-benzenediethanol,2,4-dimethyl-2-ethylenehexane-1,3-diol, 2-butane-1,4-diol, and polyolssuch as trimethylolethane, trimethylolpropane, trimethylolhexane,triethylolpropane, 1,2,4-butanetriol, glycerol, pentaerythritol,dipentaerythritol, etc.

Typically, the reaction between the polyols and the polycarboxylic acidsis conducted at about 120° C. to about 200° C. in the presence of anesterification catalyst such as dibutyl tin oxide.

1.A.3. Additionally, hydroxy-functional polymers can be prepared by thering opening reaction of epoxides and/or polyepoxides with primary or,preferably, secondary amines or polyamines to produce hydroxy-functionalpolymers. Representative amines and polyamines include ethanol amine,N-methylethanol amine, dimethyl amine, ethylene diamine, isophoronediamine, etc. Representative polyepoxides include those prepared bycondensing a polyhydric alcohol or polyhydric phenol with anepihalohydrin, such as epichlorohydrin, usually under alkalineconditions. Some of these condensation products are availablecommercially under the designations EPON or DRH from Shell ChemicalCompany, and methods of preparation are representatively taught in U.S.Pat. Nos. 2,592,560; 2,582,985 and 2,694,694.

1.A.4. Other useful hydroxy-functional polymers can be prepared by thereaction of an excess of at least one polyol, such as thoserepresentatively described in Section 1.A.2 above, with polyisocyanatesto produce hydroxy-functional urethanes. The polyols should, of course,be present at a level to provide an excess of hydroxyl groups overisocyanate groups. Representative polyisocyanates having two or moreisocyanate groups per molecule include the aliphatic compounds such asethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene,1,2-propylene, 1,2-butylene, 2,3-butylene, 1,3-butylene, ethylidene andbutylidene diisocyanates; the cycloalkylene compounds such as3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate, and the1,3-cyclopentane, 1,3-cyclohexane, and 1,2-cyclohexane diisocyanates;the aromatic compounds such as m-phenylene, p-phenylene, 4,4'-diphenyl,1,5-naphthalene and 1,4-naphthalene diisocyanates; thealiphatic-aromatic compounds such as 4,4'-diphenylene methane, 2,4- or2,6-toluene, or mixtures thereof, 4,4'-toluidine, and 1,4-xylylenediisocyanates; the nuclear substituted aromatic compounds such asdianisidine diisocyanate, 4,4'-diphenylether diisocyanate andchlorodiphenylene diisocyanate; the triisocyanates such as triphenylmethane-4,4',4"-triisocyanate, 1,3,5-triisocyanate benzene and2,4,6-triisocyanate toluene; and the tetraisocyanates such as4,4'-diphenyl-dimethyl methane-2,2'-5,5'-tetraisocyanate; thepolymerized polyisocyanates such as toluene diisocyanate dimers andtrimers, and other various polyisocyanates containing biuret, urethane,and/or allophanate linkages. The polyisocyanates and the polyols aretypically reacted at temperatures of 25° C. to about 150° C. to form thehydroxy-functional polymers.

1.A.5. Useful hydroxy-functional polymers can also be convenientlyprepared by free radical polymerization techniques such as in theproduction of acrylic resins. The polymers are typically prepared by theaddition polymerization of one or more monomers. At least one of themonomers will contain, or can be reacted to produce, a reactive hydroxylgroup. Representative hydroxy-functional monomers include 2-hydroxyethylacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate,2-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, 4-hydroxypentylacrylate, 2-hydroxyethyl ethacrylate, 3-hydroxybutyl methacrylate,2-hydroxyethyl chloroacrylate, diethylene glycol methacrylate,tetraethylene glycol acrylate, para-vinyl benzyl alcohol, etc. Typicallythe hydroxy-functional monomers would be copolymerized with one or moremonomers having ethylenic unsaturation such as:

(i) esters of acrylic, methacrylic, crotonic, tiglic, or otherunsaturated acids such as: methyl acrylate, ethyl acrylate, propylacrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate,ethylhexyl acrylate, amyl acrylate, 3,5,5-trimethylhexyl acrylate,methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobornylmethacrylate, dimethylaminoethyl methacrylate, ethyl tiglate, methylcrotonate, ethyl crotonate, etc.;

(ii) vinyl compounds such as vinyl acetate, vinyl propionate, vinylbutyrate, vinyl isobutyrate, vinyl benzoate, vinyl m-chlorobenzoate,vinyl p-methoxybenzoate, vinyl alpha-chloroacetate, vinyl toluene, vinylchloride; etc.;

(iii) styrene-based materials such as styrene, alpha-methyl styrene,alpha-ethyl styrene, alpha-bromo styrene, 2,6-dichlorostyrene, etc.;

(iv) allyl compounds such as allyl chloride, allyl acetate, allylbenzoate, allyl methacrylate, etc.;

(v) other copolymerizable unsaturated monomers such as acrylonitrile,methacrylonitrile, dimethyl maleate, isopropenyl acetate, isopropenylisobutyrate, acrylamide, methacrylamide, and dienes such as1,3-butadiene, etc.

The polymers are conveniently prepared by conventional free radicaladdition polymerization techniques. Frequently, the polymerization willbe initiated by conventional initiators known in the art to generate afree radical such as azobis(isobutyrontrile), cumene hydroperoxide,t-butyl perbenzoate, etc. Typically, the monomers are heated in thepresence of the initiator at temperatures ranging from about 35° C. toabout 200° C., and especially 75° C. to 150° C., to effect thepolymerization. The molecular weight of the polymer can be controlled,if desired, by the monomer selection, reaction temperature and time,and/or the use of chain transfer agents as is well known in the art.

Especially preferred polymers in the practice of this invention forreaction with the cyclic anhydride to produce the carboxylicacid-functional polymers are hydroxy-functional polyesters andhydroxy-functional free radical addition polymers. An especiallypreferred hydroxy-functional polymer is the addition polymerizationreaction product of (a) 10 to about 40 weight percent of ahydroxy-functional ethylenically unsaturated monomer and (b) 60 to about90 weight percent of at least one ethylenically unsaturated monomercopolymerizable with the hydroxy-functional monomer.

The cyclic carboxylic acid anhydrides useful in the practice of thisinvention to produce the carboxylic acid-functional half-ester productby reaction with the hydroxy-functional compound can be any monomericaliphatic or aromatic cyclic anhydride having one anhydride group permolecule. Representative anhydrides include, phthalic anhydride,3-nitrophthalic anhydride, 4-nitrophthalic anhydride, 3-fluorophthalicanhydride, 4-chlorophthalic anhydride, tetrachlorophthalic anhydride,tetrabromophthalic anhydride, tetrahydrophthalic anhydride,hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, succinicanhydride, dodecenylsuccinic anhydride, octylsuccinic anhydride, maleicanhydride, dichloromaleic anhydride, glutaric anhydride, adipicanhydride, chlorendic anhydride, itaconic anhydride, citraconicanhydride, endomethylenetetrahydrophthalic anhydride,cyclohexane-1,2-dicarboxylic anhydride, 4-cyclohexene-1,2-dicarboxylicanhydride, 4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride,5-norbornene-2,3-dicarboxylic anhydride,1,4-cyclohexadiene-1,2-dicarboxylic anhydride,1,3-cyclopentanedicarboxylic anhydride, diglycolic acid anhydride, etc.Maleic anhydride is especially preferred because of its reactivity andrelatively low cost. Other useful anhydrides include those anhydrideshaving a free carboxyl group in addition to the anhydride group such astrimellitic anhydride, aconitic anhydride, 2,6,7-naphthalenetricarboxylic anhydride, 1,2,4-butane tricarboxylic anhydride,1,3,4-cyclopentane tricarboxylic anhydride, etc.

The reaction of the hydroxy-functional compound and the cyclic anhydrideshould normally be conducted at temperatures less than about 75° C.,preferably less than 65° C., and most preferably between about 35° C. to60° C. The reaction temperature is maintained until the reaction hasproceeded to provide the desired amount of half-ester groups on theacid-functional compound. Normally, as a convenient measure of theextent of the reaction, the reaction will be continued until no chargein the amount of residual unreacted anhydride can be observed, and willgenerally involve reacting at least about 70%, and preferably at least95%, of the available anhydride. If the subsequent end use of theacid-functional polymer can tolerate the remaining free anhydride, ifany, no separation or removal of the excess unreacted anhydride isnecessary. If the end use of the acid-functional polymer requires thatit be free of any unreacted anhydride, the reaction can be continueduntil substantially all of the anhydride has reacted, or the freeanhydride may be removed by vacuum distillation or other technique wellknown in the art.

The level of anhydride reacted with the hydroxy-functional compound needonly be sufficient to provide the final desired acid value of the acidfunctional compound. Typically the reaction would be conducted byadmixing the polyol and the anhydride at levels to provide at leastabout 0.3 and normally about 0.7 to 1.0 anhydride groups for eachhydroxyl group. By conducting the reaction at temperatures less thanabout 75° C. the carboxylic acid groups formed as part of the half-esterare not appreciably reactive with the hydroxyl groups themselves and sothey do not compete with the ring opening half-ester reaction of theremaining anhydrides.

In order to conduct the reaction at these relatively low temperatures,it is preferred to utilize an esterification catalyst. The catalystshould be present in sufficient amount to catalyze the reaction andtypically will be present at a level of at least about 0.01%, andnormally from about 0.05% to about 3.0%, based upon the weight of thecyclic anhydride. Catalysts which are useful in the esterificationreaction of the anhydride with the hydroxy-functional molecule includemineral acids such as hydrochloric acid and sulfuric acid; alkali metalhydroxides such as sodium hydroxide; tin compounds such as stannousoctoate, or dibutyltin oxide; aliphatic or aromatic amines, especiallytertiary alkyl amines, such as triethylamine; and aromatic heterocyclicamines such as N-methyl imidazole and the like. Especially preferred areN-methyl imidazole and triethylamine.

Although the reaction between the hydroxy-functional compound and theanhydride can be conducted in the absence of solvent if the materialsare liquid at the reaction temperature, it is normally preferred toconduct the reaction in the presence of an inert solvent such as esters,ketones, ethers or aromatic hydrocarbons. If desired, theacid-functional molecule can be utilized as the solvent solution, or,optionally, all or part of the insert solvent may be removed, e.g. bydistillation, after the reaction is completed.

After the reaction is completed it is frequently desirable to add a lowmolecular weight alcohol solvent, such as isobutanol or isopropanol, tothe acid-functional polymer at a level of about 5 to 35% by weight toprovide stabilization on storage.

1.B. Carboxylic Acid-Functional Polymers Prepared from UnsaturatedAcid-Functional Monomers

Useful acid-functional polymers can also be conveniently prepared byaddition polymerization techniques such as in the production of acrylicresins. The acid-functional polymers are routinely prepared by the freeradical addition polymerization of unsaturated acids such as maleicacid, acrylic acid, methacrylic acid, crotonic acid, etc. along with oneor more unsaturated monomers. Representative monomers include the estersof unsaturated acids, vinyl compounds, styrene-based materials, allylcompounds and other copolymerizable monomers as representatively taughtin Section 1.A.5. of this specification. The monomers which areco-polymerized with the unsaturated acid should be free of anyfunctionality which could react with the acid groups during thepolymerization.

1.C. Carboxylic Acid-Functional Polymers Prepared from Polyols andPolyacids

Other useful acid-functional polymers include polyester polymersobtained from the reaction of one or more aromatic and/or aliphaticcarboxylic acids or their anhydrides and one or more aliphatic and/oraromatic polyols wherein the acid functionality is present at a level toprovide an excess of acid groups over hydroxyl groups. Representativecarboxylic acids and polyols include those listed in Section 1.A.2. ofthis specification.

2. Anhydride-Functional Compounds

The anhydride-functional compounds which are useful in the practice ofthis invention can be any aliphatic or aromatic compound having at leasttwo cyclic carboxylic acid anhydride groups in the molecule. Polymericanhydrides having number average molecular weights between 500 and 7,000are most useful. Especially preferred in the practice of this inventionis the use of free radical addition polymers, such as acrylic polymershaving anhydride functionality. These are conveniently prepared as iswell known in the art by the polymerization under free radical additionpolymerization conditions of at least one unsaturated monomer havinganhydride functionality, such as maleic anhydride, citraconic anhydride,itaconic anhydride, propenyl succinic anhydride, etc. with otherethylenically unsaturated monomers such as the esters of unsaturatedacids, vinyl compounds, styrene-based materials, allyl compounds andother copolymerizable monomers, all as representatively taught inSection 1.A.5. of this specification. The monomers which arecopolymerized with the unsaturated anhydride should, of course, be freeof any functionality which could react with the anhydride group duringthe polymerization. The anhydride-functional polymers can beconveniently prepared by conventional free radical additionpolymerization techniques. Typically the polymerization will beconducted in an inert solvent and in the presence of a catalyst attemperatures ranging from 35° C. to about 200° C. An especiallypreferred anhydride-functional polymer comprises the free radicaladdition polymerization product of (a) 5 to 40, and especially 15 toabout 25, weight percent of an ethylenically unsaturated monoanhydrideand (b) 60 to 95, and especially 75 to about 85, weight percent of atleast one other ethylenically unsaturated monomer copolymerizable withthe ethylenically unsaturated anhydride.

Other polyanhydrides, in addition to the polymeric anhydrides preparedby a free radical addition process, can also be utilized in the practiceof this invention. Ester anhydrides can be prepared, as is known in theart, by the reaction of e.g. trimellitic anhydride with polyols. Otherrepresentative, suitable polyanhydrides include poly-functional cyclicdianhydrides such as cyclopentane tetracarboxylic acid dianhydride,diphenyl-ether tetracarboxylic acid dianhydride, 1,2,3,4,-butanetetracarboxylic acid dianhydride, and the benzophenone tetracarboxylicdianhydrides such as 3,3',4,4'-benzophenone tetracarboxylic dianhydride,and 2,bromo-3,3',4,4'-benzophenone tetracarboxylic acid dianhydride.Trianhydrides such as the benzene and cyclohexane hexacarboxylic acidtrianhydrides are also useful.

Additionally, useful polyanhydrides can be prepared by the maleinizationof polyunsaturated compounds such as unsaturated rubbers, unsaturatedoils and unsaturated hydrocarbons.

3. Epoxy-Functional Compounds

The coatings of this invention also require the use of at least oneepoxy-functional compound. The epoxy compounds can be monoepoxies or,preferably, a polyepoxide having an average of at least two epoxy groupsper molecule.

Representative useful monoepoxides include the monoglycidyl ethers ofaliphatic or aromatic alcohols such as butyl glycidyl ether, octylglycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, dodecylglycidyl ether, p-tert-butylphenyl glycidyl ether, and o-cresyl glycidylether. Monoepoxy esters such as the glycidyl ester of versatic acid(commercially available as CARDURA® E from Shell Chemical Company), orthe glycidyl esters of other acids such as tertiary-nonanoic acid,tertiary-decanoic acid, tertiary-undecanoic acid, etc. are also useful.Similarly, if desired, unsaturated monoepoxy esters such as glycidylacrylate, glycidyl methacrylate or glycidyl laurate could be used.Additionally, monoepoxidized oils can also be used.

Other useful monoepoxies include styrene oxide, cyclohexene oxide,1,2-butene oxide, 2,3-butene oxide, 1,2-pentene oxide, 1,2-hepteneoxide, 1,2-octene oxide, 1,2-nonene oxide, 1,2-decene oxide, and thelike.

It is only necessary that the monoepoxide compounds have a sufficientlylow volatility to remain in the coating composition under the applicableconditions of cure.

Polyepoxides are especially preferred in this reaction. Especiallypreferred as the poly-functional epoxy compounds, due to theirreactivity and durability, are the polyepoxy-functional cycloaliphaticepoxies. Preferably, the cycloaliphatic epoxies will have a numberaverage molecular weight less than about 2,000 to minimize theviscosity. The cycloaliphatic epoxies are conveniently prepared bymethods well known in the art such as epoxidation of dienes of polyenes,or the epoxidation of unsaturated esters by reaction with a peracid suchas peracetic and/or performic acid.

Commercial examples of representative preferred cycloaliphatic epoxiesinclude 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate (e.g."ERL-4221" from Union Carbide Corp.);bis(3,4-epoxycyclohexylmethyl)adipate (e.g. "ERL-4299" from UnionCarbide Corporation); 3,4-epoxy-6-methylcyclohexylmethyl3,4-epoxy-6-methylcyclohexane carboxylate (e.g. "ERL-4201" from UnionCarbide Corp.); bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate (e.g."ERL-4289⃡ from Union Carbide Corp.); bis(2,3-epoxycyclopentyl) ether(e.g. "ERL-0400" from Union Carbide Corp.); dipentene dioxide (e.g."ERL-4269" from Union Carbide Corp.); 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-metadioxane (e.g. "ERL-4234" from UnionCarbide Corp.). Other commercially available cycloaliphatic epoxies areavailable from Ciba-Geigy Corporation such as CY 192, a cycloaliphaticdicylidyl ester epoxy resin having an epoxy equivalent weight of about154. The manufacture of representative cycloaliphatic epoxies is taughtin various patents including U.S. Pat. Nos. 2,884,408, 3,027,357 and3,247,144.

Other polyepoxides potentially useful in the practices of this inventioninclude aliphatic and aromatic polyepoxies, such as those prepared bythe reaction of an aliphatic polyol or polyhydric phenol and anepihalohydrin. Other useful epoxies include epoxidized oils and acrylicpolymers derived from ethylenically unsaturated epoxy-functionalmonomers such as glycidyl acrylate or glycidyl methacrylate incombination with other copolymerizable monomers such as those listed in1.A.5 above. It is often desirable to utilize epoxy-functional compoundswhich are free of hydroxyl groups.

The ratios of anhydride to acid to epoxy groups can be widely variedwithin the practice of this invention. It is especially preferred,however, to provide about 0.3 to about 6.0 acid groups and about 0.6 toabout 12.0 epoxy groups for each anhydride group in the reactive system.It is especially preferred to provide 2.0 to about 5.0 acid groups and3.0 to about 8.0 epoxy groups for each anhydride group. At least one ofthe acid-functional compounds, the epoxy-functional compounds, or theanhydride-functional compounds should be a film forming polymer, andeach of the compounds should be mutually soluble with the othercompounds.

The coatings of this invention can be cured at temperatures ranging fromabout room temperature up to about 350° F. The coatings can be used asclear coatings or they may contain pigments as is well known in the art.Representative opacifying pigments include white pigments such astitanium dioxide, zinc oxide, antimony oxide, etc. and organic orinorganic chromatic pigments such as iron oxide, carbon black,phthalocyanine blue, etc. The coatings may also contain extenderpigments such as calcium carbonate, clay, silica, talc, etc.

The coatings may also contain other additives such as flow agents,catalysts, diluents, solvents, ultraviolet light absorbers, etc.

Although it is not our intent to be bound by theory, it is believed thatin the course of the curing reaction of the components of thisinvention, that at least some of the acid groups and epoxy groups reactto produce ester groups and hydroxyl groups and that at least some ofthese hydroxyl groups are reacted with the anhydride groups to produceester groups and additional acid groups. It is, therefore, especiallypreferred in the practice of this invention to include a catalyst forthe reaction of anhydride groups and hydroxyl groups and also a catalystfor the reaction of epoxy and acid groups. It is especially preferred inthe practice of this invention to utilize tertiary amines and especiallyN-methylimidazole as a catalyst for the anhydride/hydroxyl reaction. Thecatalyst for the anhydride/hydroxyl reaction will typically be presentat a level of at least 0.1% by weight of the anhydride compound andpreferably 1.0 to about 5.0%.

Tertiary amines, secondary amines such as ethyl imidazole, quaternaryammonium salts, and nucleophilic catalysts such as lithium iodide,phosphonium salts, and phosphines such as triphenyl phosphine areespecially useful as catalysts for epoxy/acid reactions. Electrophilliccatalysts, such as tin metal salts or complexes are also useful in thepractice of this invention. The catalyst for the epoxy/acid reactionwill typically be present at a level of at least 0.01% by weight of thetotal acid-functional compound and epoxy-functional compound andpreferably will be present at 0.1 to about 3.0%.

The coatings of this invention may typically be applied to any substratesuch metal, plastic, wood, glass, synthetic fibers, etc. by brushing,dipping, roll coating, flow coating, spraying or other methodconventionally employed in the coating industry. If desired, thesubstrates may be primed prior to application of the coatings of thisinvention.

One preferred application of the curable coatings of this inventionrelates to their use as clearcoats and/or basecoats inclearcoat/basecoat formulations.

Clearcoat/basecoat systems are well known, especially in the automobileindustry where it is especially useful to apply a pigmented basecoat,which may contain metallic pigments, to a substrate and allow it to forma polymer film followed by the application of a clearcoat which will notmix with or have any appreciable solvent attack upon the previouslyapplied basecoat. The basecoat composition may be any of the polymersknown to be useful in coating compositions including the reactivecompositions of this invention.

One useful polymer basecoat includes the acrylic addition polymers,particularly polymers or copolymers of one or more alkyl esters ofacrylic acid or methacrylic acid, optionally together with one or moreother ethylenically unsaturated monomers. These polymers may be ofeither the thermoplastic type or the thermosetting, crosslinking typewhich contain hydroxyl or amine or other reactive functionality whichcan be crosslinked. Suitable acrylic esters for and unsaturated monomerseither type of polymer include methyl methacrylate, ethyl methacrylate,propyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate,vinyl acetate, acrylonitrile, acrylamide, styrene, vinyl chloride, etc.Where the polymers are required to be of the crosslinking type, suitablefunctional monomers which can be used in addition to those alreadymentioned include acrylic or methacrylic acid, hydroxy ethyl acrylate,2-hydroxy propyl methacrylate, glycidyl acrylate, tertiary-butyl aminoethyl methacrylate, etc. The basecoat composition may, in such a case,also contain a crosslinking agent such as a polyisocyanate, apolyepoxide, or a nitrogen resin such as a condensate of an aldehydesuch as formaldehyde with a nitrogeneous compound such as urea, melamineor benzoguanamine or a lower alkyl ether of such a condensate. Otherpolymers useful in the basecoat composition include vinyl copolymerssuch as copolymers of vinyl esters of inorganic or organic acids, suchas vinyl chloride, vinyl acetate, vinyl propionate, etc., whichcopolymers may optionally be partially hydrolyzed so as to introducevinyl alcohol units.

Other polymers useful in the manufacture of the basecoat include alkydresins or polyesters which can be prepared in a known manner by thecondensation of polyhydric alcohols and polycarboxylic acids, with orwithout the inclusion of natural drying oil fatty acids as describedelsewhere in this specification. The polyesters or alkyds may contain aproportion of free hydroxyl and/or carboxyl groups which are availablefor reaction, if desired with suitable crosslinking agents as discussedabove.

If desired, the basecoat composition may also contain minor amounts of acellulose ester, to alter the drying or viscosity characteristics of thebasecoat.

Typically, the basecoat will include pigments conventionally used forcoating compositions and after being applied to a substrate, which mayor may not previously have been primed, the basecoat will be allowedsufficient time to form a polymer film which will not be lifted duringthe application of the clearcoat. The basecoat may be heated or merelyallowed to air-dry to form the film. Generally, the basecoat will beallowed to dry for about 1 to 20 minutes before application of theclearcoat. The clearcoat is then applied to the surface of the basecoat,and the system can be allowed to dry at room temperature or, if desired,can be force dried by baking the coated substrate at temperaturestypically ranging up to about 350° F.

Typically, the clearcoat may contain ultraviolet light absorbers such ashindered phenols or hindered amines at a level ranging up to about 6% byweight of the vehicle solids as is well known in the art. The clearcoatcan be applied by any application method known in the art, butpreferably will be spray applied. If desired, multiple layers ofbasecoat and/or clearcoat can be applied. Typically, both the basecoatland the clearcoat will each be applied to give a dry film thickness ofabout 0.01 to about 6, and especially about 0.5 to about 3.0 mils.

If desired, the novel reactive compositions taught herein could be usedas a basecoat, in which case the clearcoat could also comprise the novelreactive coatings taught herein, or the polymers taught herein as beinguseful as basecoat formulations could be utilized as clearcoats.

The following examples have been selected to illustrate specificembodiments and practices of advantage to a more complete understandingof the invention. Unless otherwise stated, "parts" means part-by-weightand "percent" is percent-by-weight. The numeric ratings for solventresistance (MEK rubs), wet adhesion, and salt spray are on a scale of0-10, 10 best.

In each of the clearcoat/basecoat formulations described in Examples 25through 34 the primer was G.G.P.® etching primer filler (2-componentvinyl-butyral based primer commercially available from TheSherwin-Williams Company) and the basecoat was Acrylyd® acrylic enamel(a lacquer-like coating commercially available from The Sherwin-WilliamsCompany). The primer, the basecoat and the clearcoat were applied toprovide dry film thicknesses of 1.0, 1.0 and 2.0 mils respectively.

EXAMPLE 1 Preparation of Anhydride-Functional Polymer

A reaction vessel equipped with mechanical stirrer, reflux condenser,thermometer, nitrogen inlet and fluid metering pump was charged with1472 parts xylene, 240 parts maleic anhydride and heated to reflux (139°C.) under nitrogen. A monomer mixture of 480 parts isobutylmethacrylate, 720 parts butyl acrylate, 720 parts methyl methacrylate,120 parts maleic anhydride and 60 parts t-butyl perbenzoate were thenmetered into the reaction over a 3-hour period. Halfway through theaddition, an additional 120 parts of maleic anhydride was charged to thereaction vessel and monomer addition is continued. After refluxing thereaction mixture for an additional 15 minutes, 12 parts of t-butylperbenzoate in 128 parts xylene was added over 45 minutes. Heating wascontinued for 2 hours at reflux. The resulting xylene solubleanhydride-functional resin was 61.2% solids, had a Gardner Holdtviscosity of 24.5, an acid value of 116.5 and a density of approximately8.6 pounds per gallon.

EXAMPLE 2 Anhydride-Functional Acrylic Polymer

A reaction vessel equipped as in Example 1 was charged with 6,624 partsof xylene, 648 parts of maleic anhydride and heated to reflux undernitrogen. To this heated solution a monomer mixture of 5,616 parts butylacrylate, 3,024 parts methylmethacrylate, 540 parts maleic anhydride and270 parts of t-butyl peroctoate was metered into the reaction vessel ata constant rate over a 3-hour time period. At 1 hour and at 2 hours intothe monomer addition, heating and monomer addition was stopped and thereactor was charged with 540 parts and 432 parts of maleic anhydriderespectively. Heating was resumed to reflux and the monomer addition wascontinued. The reaction mixture was maintained at reflux temperature foran additional 15 minutes after the completion of all of the monomeraddition. A solution of 54 parts of t-butyl peroctoate in 576 partsxylene was added to the reaction over a 45-minute period. The reactionwas held at reflux for an additional 2 hours and then allowed to cool toroom temperature to obtain an anhydride-functional polymer having anumber average molecular weight of about 1,800 and a free maleicanhydride content of less than 0.1%. This polymer had an average ofabout 3.6 anhydride groups per molecule.

EXAMPLE 3 Carboxyl-Functional Acrylic Polymer

A carboxyl-functional acrylic polymer was prepared by charging areaction vessel equipped with a mechanical stirrer, reflux condenser,thermometer, nitrogen inlet and fluid metering pump with 1621.2 partsxylene which was then heated at 120° C. under nitrogen. A monomermixture comprising 1013.2 parts hydroxy ethyl acrylate, 1013.2 partsTone M-100 (trade name of Union Carbide's hydroxy acrylic/caprolactoneadduct believed to be the reaction product of 1 mole of hydroxyl ethylacrylate and 2 moles of caprolactone), 2837.2 parts methyl methacrylate,3242.1 parts isobutyl methacrylate, 81.1 parts Vazo 67 (trademark forE.I. duPont initiator believed to be 2,2'-azobis(2-methylbutyronitrile))and 6352.9 parts xylene was metered into the reaction vessel over aperiod of 3 hours while maintaining the temperature of the reactionvessel at 120° C. After the monomer addition was completed, thetemperature of the reaction mixture was raised to reflux (137° C.) and20.3 parts Vazo 67 in 131.4 parts xylene was added over a period of 30minutes. Reflux temperature was maintained for one additional hour.After cooling the reaction mixture to room temperature, 1144.4 partsmaleic anhydride and 1144.4 parts xylene were added. The polymericsolution was heated to 60° C. and 10.8 parts triethyl amine was added.The reaction mixture was stirred and maintained at 60° C. forapproximately 6 hours. The resulting carboxylic acid-functional acrylicpolymer had a theoretical percent solids of 48.1, a Gardner Holdtviscosity of V-, and an acid equivalent weight of 790.

EXAMPLE 4

A curable coating was prepared according to the following recipe:

    ______________________________________                                        Raw Material            Parts                                                 ______________________________________                                        Acid-Functional Acrylic Resin                                                                         411.85                                                of Example 3                                                                  ERL 4221 (Union Carbide trade name                                                                    131.13                                                for 3,4-epoxycyclohexylmethyl                                                 3,4-epoxycyclohexane carboxylate)                                             10% Triphenylphosphine/Toluene                                                                         33.28                                                Xylene                   74.58                                                Anhydride-Functional Polymer of                                                                       151.54                                                Example 1                                                                     10% N-methylimidazole/   32.65                                                Methyl Isobutyl Ketone                                                        ______________________________________                                    

This coating formulation represented approximately 1.5 epoxy groups pereach theoretical acid group and the triphenylphosphine catalyst waspresent at approximately 1% on epoxy and carboxyl resin solids.

The coatings were applied directly to iron phosphate treated steelsubstrates and allowed to air dry. The coated films exhibited a Knoophardness number of 14 after one day, 25 after two days, 36 after oneweek, and 71 after two weeks. The cured films had good solventresistance, excellent resistance to humidity (170 hours) and to saltspray (170 hours).

EXAMPLE 5

A curable coating was prepared according to the following recipe:

    ______________________________________                                        Raw Material              Parts                                               ______________________________________                                        Acid-Functional Acrylic Resin                                                                           409.08                                              of Example 3                                                                  Anhydride-Functional Acrylic Polymer                                                                    129.35                                              of Example 2                                                                  ERL 4299 (Union Carbide Trade Name                                                                      107.00                                              for bis(3,4-epoxycyclohexylmethyl)adipate)                                    Byk 300 (flow agent commercially available                                                               2.50                                               from Byk Mallinkrodt Chem. Produkte GmbH.)                                    Xylene                     49.78                                              Methyl ethyl ketone       100.20                                              20% N-methylimidazole in methyl isobutyl ketone                                                          19.55                                              ______________________________________                                    

This coating represents 3.3 epoxy groups and 1.6 carboxylic acid groupsper each anhydride group. The N-methylimidazole catalyst is present at1% based upon resin solids. The coatings were applied directly to ironphosphate treated cold rolled steel panels and allowed to air dry atroom temperature for 24 hours. The coated films exhibited a KoenigPendulum hardness number of 65 after 1 week and 113 after 4 weeks.Solvent resistance (MEK) was rated as a 9 after 1 week air dry. Thefilms showed good humidity and salt spray resistance.

EXAMPLES 6-14

Coating formulations were prepared according to the recipe of Example 5except that the levels of acid-functional resin, anhydride-functionalresin, and epoxy-functional resin were varied as shown in the tablebelow:

                                      TABLE 1                                     __________________________________________________________________________    Air Dry                                                                                                                         Comparative Examples                                                          Commercially Available      Example    6    7   8   9   10   11  12  13  14   Two-Component               __________________________________________________________________________                                                      Urethane                    Component Eq.                                                                 COOH         0.1                                                                                1.0                                                                               9.9                                                                               0.1                                                                               1.0                                                                                0.8                                                                               0.5                                                                               0.3                                                                               0.3                                                                              --                          Epoxy        1.5                                                                                1.0                                                                               14.8                                                                              1.2                                                                               2.7                                                                                2.0                                                                               1.8                                                                               1.6                                                                               1.3                                                                              --                          Anh          1.0                                                                                1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                                1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                              --                          KPH                                                                           1 week     43   64  48  57  54   71  56  55  64   73                          4 weeks    104  109 60  110 106  105 102 107 115  99                          MEK (0-10, 10 Best)                                                           1 week      8    5   9   6   8    5   4   8   5   10                          4 weeks     9    7  10   7   9    6   7   8   7   10                          Humidity                                                                      Init. 20°                                                                         93   90  93  95  91   79  25  53  60   98                          Final 20°                                                                         88   83  25  93  91   77  25  53  54   97                          % Retention                                                                               95%  92%                                                                               27%                                                                               98%                                                                               100%                                                                               97%                                                                               100%                                                                              100%                                                                              90%  99%                        Salt Spray                                                                    Scribe Creep (mm)                                                                         6   11  15  10   4    5  12  17  10    5                          Scribe Corrosion                                                                          2    0   4   0   8    2   0   0   0    5                          (1-10, 10 Best)                                                               __________________________________________________________________________

EXAMPLES 15-24

Coating compositions as described in Examples 6-14 were spray applied toiron phosphate treated cold rolled steel panels and baked 30 minutes at180° F. to give the performance described in Table 2 below:

                                      TABLE 2                                     __________________________________________________________________________    180° F./30-Minute Bake                                                                                                    Comparative Examples                                                          Commercially                                                                  Available to               Example    15  16  17  18  19  20  21  22  23  24  Component                  __________________________________________________________________________                                                       Urethane                   Component Eq.                                                                 COOH         0.1                                                                               0.1                                                                               9.9                                                                               0.1                                                                               1.0                                                                               0.8                                                                               0.5                                                                               0.3                                                                               0.3                                                                               1.6                                                                             --                         Epoxy        1.5                                                                               1.0                                                                               14.8                                                                              1.2                                                                               2.7                                                                               2.0                                                                               1.8                                                                               1.6                                                                               1.3                                                                               3.3                                                                             --                         Anh          1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                             --                         KPH                                                                           1 week     22  41  65  32  51  63  41  25  37  67  129                        4 weeks    80  100 72  88  90  104 72  71  71  101 135                        MEK (0-10, 10 Best)                                                           1 week      6   3   9   4   9   6   6   5   4   9  10                         4 weeks     6   7   9   6  10   8   8   8   7   9  10                         Humidity                                                                      Init. 20°                                                                         69  77  91  60  87  33   7   6   7  100 99                         Final 20°                                                                         67  63  55  51  88  46   9   6   7  99  96                         % Retention                                                                               97%                                                                               82%                                                                               60%                                                                               85%                                                                               101%                                                                              117%                                                                              78%                                                                               100%                                                                              100%                                                                              99%                                                                               97%                       Wet Adhesion                                                                             10  10   7  10  10  10  10  10  10  10  10                         (0-10, 10 Best)                                                               Salt Spray                                                                    Scribe Creep (mm)                                                                         7  20  13  10   9  15  19  16  10   9   2                         Scribe Corrosion                                                                          2   0   5   0   8   0   0   0   0   5   5                         (0-10, 10 Best)                                                               __________________________________________________________________________

EXAMPLES 25-34

Clearcoat/basecoat systems were prepared utilizing the reactive coatingof this invention as a clearcoat by reducing the clear coatings of thisinvention with suitable solvents and spray applying these coatings overa primer/basecoat system on iron phosphate treated cold rolled steelpanels. The coating system was allowed to ambient cure at least 24 hoursbeing testing. The results of testing are shown in Table 3 below:

                                      TABLE 3                                     __________________________________________________________________________                                                       Comparative Examples                                                          Commercially                                                                  Available Two-             Example    25  26  27  28  29  30  31  32  33  34  Component                  __________________________________________________________________________                                                       Urethane                   Component Eq.                                                                 COOH         0.1                                                                               0.1                                                                               9.9                                                                               0.1                                                                               1.0                                                                               0.8                                                                               0.5                                                                               0.3                                                                               0.3                                                                               1.6                                                                             --                         Epoxy        1.5                                                                               1.0                                                                               14.8                                                                              1.2                                                                               2.7                                                                               2.0                                                                               1.8                                                                               1.6                                                                               1.3                                                                               3.3                                                                             --                         Anh          1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                               1.0                                                                             --                         KPH                                                                           1 week     28  36  15  35  22  22  25  40  42  29  28                         4 weeks    59  62  26  61  38  37  54  69  69  40  41                         MEK (0-10, 10 Best)                                                           1 week      3   2   3   2   6   6   6   3   3   3  10                         4 weeks     9   2   3   2   8   6   7   8   7   3  10                         Humidity                                                                      Init. 20°                                                                         80  76  80  70  78  72  38  55  62  80  83                         Final 20°                                                                         73  62  53  67  70  50  33  47  36  73  81                         % Retention                                                                               91%                                                                               82%                                                                               66%                                                                               96%                                                                               90%                                                                               69%                                                                               87%                                                                               85%                                                                               58%                                                                               91%                                                                               98%                       Wet Adhesion                                                                              8   9   0  10   2   5   5   8   7   5   8                         (0-10, 10 Best)                                                               Salt Spray                                                                    Scribe Creep (mm)                                                             NONE -                                                                        Scribe Corrosion                                                                          7   9   8   7   9   9    9.5                                                                              8   9   8    7                        (0-10, 10 Best)                                                               __________________________________________________________________________

While this invention has been described by a specific number ofembodiments, it is obvious that other variations and modifications maybe made without departing from the spirit and scope of the invention asset forth in the appended claims.

We claim:
 1. In a substrate coated with a multi-layer decorative and/orprotective coating which comprises:(a) a basecoat comprising a pigmentedfilm-forming polymer; and (b) a transparent clearcoat comprising afilm-forming polymer applied to the surface of the basecoatcomposition;the improvement which comprises utilizing as the clearcoatand/or the basecoat a multicomponent curable composition which isreactive upon mixing of the components, wherein the curable compositioncomprises: (i) an acid-functional polymer having an average of at leasttwo carboxylic acid groups per molecule and wherein the polymer isobtained by the half-ester reaction of a hydroxy-functional polymer witha cyclic carboxylic acid anhydride; and (ii) an anhydride-functionalpolymer having an average of at least two cyclic carboxylic acidanhydride groups per molecule and wherein the anhydride-functionalpolymer is the addition polymerization reaction product of (a) 5 toabout 40 weight percent of an ethylenically unsaturated monoanhydrideand (b) 60 to about 95 weight percent of at least one otherethylenically unsaturated monomer copolymerizable with the ethylenicallyunsaturated anhydride; and (ii) an epoxy-functional compound having anaverage of at least two cycloalophatic epoxy groups per molecule.